At present concentration of 92235U in naturally occurring ur

At present, concentration of 92235U in naturally occurring uranium deposits is approximately 0.71 %. What will the concentration be 1.9 billion years from now? The half-life of 92235U is T1/2 = 7 × 108 years. (State your answer in percent, do not insert a unit.)

Solution

We know that N_t = N_o * (1/2)^(t/t_1/2)

Given N_o = 0.0071,

t_1/2 =7×10^8 yrs = 0.7x10^9 years,

t = 1.7x10^9 years

We need to calculate N_t i.e the concentration after time \'t\'.

We have, t/t_1/2 = 1.9/0.7 = 2.71

=> N_t = 0.0071*(0.5^2.71)

= 0.001085 = 0.1085% (Answer)